Electronic article surveillance (“EAS”) systems are detection systems that allow the identification of a marker or tag within a given detection zone. EAS systems have many uses, but most often they are used as security systems for preventing shoplifting in stores or removal of property in office buildings. EAS systems come in many different forms and make use of a number of different technologies.
A typical EAS system includes an electronic detection unit, tags and/or markers, and a detacher or deactivator. The detection units can, for example, be formed as pedestal units, buried under floors, mounted on walls, or hung from ceilings. The detection units are usually placed in high traffic areas, such as entrances and exits of stores or office buildings. The tags and/or markers have special characteristics and are specifically designed to be affixed to or embedded in merchandise or other objects sought to be protected. When an active tag passes through a tag detection zone, the EAS system sounds an alarm, a light is activated and/or some other suitable alert devices are activated to indicate the removal of the tag from the prescribed area.
Radio-frequency identification (“RFID”) systems are also generally known in the art and may be used for a number of applications, such as managing inventory, electronic access control, security systems, and automatic identification of cars on toll roads. An RFID system typically includes an RFID reader and an RFID device. The RFID reader may transmit a radio-frequency (“RF”) carrier signal to the RFID device. The RFID device may respond to the carrier signal with a data signal encoded with information stored by the RFID device.
The market need for combining EAS and RFID functions in the retail environment is rapidly emerging. Many retail stores that now have EAS for shoplifting protection rely on bar code information for inventory control. RFID offers faster and more detailed inventory control over bar coding. Retail stores already pay a considerable amount for hard tags that are re-useable. Adding RFID technology to EAS systems can easily pay for the added cost due to improved productivity in inventory control as well as loss prevention.
An important consideration in designing RFID tags is to include EAS functionality, such as including the ability to deactivate or “kill” a tag as well as the ability to reactivate the tag. Failure to deactivate (“FTD”) is a major complaint affecting all EAS detection platforms. This undesirable side effect poses a serious confidence issue to system users, who inadvertently grow accustomed to “deactivated” tags triggering an alarm, thus, ignoring valid alarm events where live tags are involved. This phenomenon occurs when a tag, or label, is not properly deactivated and still carries some properties of a live tag.
However, designing an RFID tag with the capability to detect “kill” and reactivate commands from an RFID reader is not without inherent difficulties. The ability to recognize and decode these commands requires more complex logic and a large number of logic gates, thus increasing the complexity and costs associated with manufacturing ASICs for use in RFID tags. There have been other attempts to address this issue. Tags using EPC-CIG2 or ISO1800-6C protocols use multiple configuration settings, larger memory usage, and multiple interface functions. Although these protocols allow for EAS functionality, they do so with complex designs and prohibitively expensive die costs. Other RFID solutions implement very simple tag protocols and memory formats that may reduce die costs but these protocols provide inadequate performance and generally do not allow the tag to implement EAS features. Including an EAS bit that can be verified by the RFID reader does not solve the problem because once “killed” the tag is “dead” and cannot be read. Only a reactivate command issued by the interrogator re-commissions the tag for use.
At least part of the prohibitive costs associated with designing tags to decode incoming interrogation commands to “kill’ or reactivate an RFID tag is due to the design of the ASIC within the RFID tag. Going through each bit of information in the interrogation signal requires complex design schemes since every single bit of information in the signal must be decoded in order for the tag to properly identify what command is being sent. This requires a large number of logic gates to read and decode each bit of information that is transmitted by the RFID reader, rending present decoding schemes impractical due to the exorbitant costs associated with such designs.
What is therefore needed is a simplified and streamlined decoding process that will permit the RFID tag to enable EAS functionality by efficiently determining the identity of the commands transmitted by the RFID reader thus reducing the complexity and costs associated with ASIC design.